Ignition test probe

Abstract

A self-contained handheld peak ignition breakdown voltage probe locates faulty sparkplugs in an internal combustion engine. The probe has a novel dual-polarity detection system suitable for all ignition systems, distributorless or distributor types. Each nanosecond peak breakdown ignition event is signalled by a high-intensity LED lamp lit for a fixed period of time. An adjustable calibrated threshold level provides precise control of acceptance level. Other problems such as cabling, plug gap, and relative compression may also be inferred. The simple arrangement of integrated circuits provides a novel and useful tool for locating ignition problems.

I claim: 
     
       1. A compact dual polarity handheld self-contained active proximity electrical peak voltage signal detecting probe comprising: capacitive coupling means for coupling the probe to a sparkplug cable to sense said ignition peak voltage signal;   an undistorted low level analog means of said ignition peak voltage signal comprising a resistive capacitive network connected to said capacitive coupling means providing an undistorted low level analog signal wherein the resistors of said network are noninductive resistors;   an isolation amplifier means responsive to said undistorted low level analog signal to provide an isolated signal output;   an expanded manually controlled attenuation means connected to said isolation amplifier output providing an expanded controlled level signal of the isolated analog signal whereby precise control of signal level is obtained;   an absolute dual comparator means having dual polarity references and dual polarity inputs, wherein said dual polarity inputs are connected to said expanded manually controlled calibrated attenuation means to provide common output magnitude comparisons independent of said ignition peak signal polarity;   a fixed pulse time means responsive to an output of said absolute dual comparator means to provide a fixed pulse time when the controlled level signal exceeds either dual polarity reference level;   an high intensity light means responsive to said fixed pulse time means providing a visual indication of said ignition peak voltage signal said ignition peak voltage signal are converted to millisecond light signals suitable for daylight viewing.   
     
     
       2. The devices of claim 1 further comprising: an expanded manually calibrated dial means controlling said expanded controlled attenuation means providing indications of relative level of said ignition peak voltage signal, said relative level being signalled by adjustment of said expanded calibrated dial and said high intensity light means whereby highest accuracy is obtained.   
     
     
       3. The device of claim 1 further comprising: a means for operator detection of said ignition peak voltages comprising operator adjustment of said expanded manually controlled attenuation means for display of said high intensity light means responsive to said absolute comparator whereby the signal detected by the probe is independent of said ignition system polarity and is particularly useful in the test of dual polarity nondistributor ignition system.